No Arctic Air In Mix This Week But Coldest Air Of Season Next Week For Montana

Written by on October 15, 2012 in North and South America, United States of America with 0 Comments


Like we saw over the weekend with a storm pushing into California and crossing the Plains, another system comes acalling into the Pacific Northwest by late Wed-Thurs and intensifies as it enters the Plains. By Thursday, the severe threat is likely back over the Plains/Midwest while fresh snows fall over the Rockies.

The Pacific jet has intensified across the US with arctic air back north. While a chilly trough drops into the Southeast this weekend, this air is maritime polar and not arctic. In saying that, Gulf of Alaska storms can bring is very sufficient air nonetheless to produce heavy Intermountain West snowfalls and we will see this substantially over the next 2 weeks. Arctic air will reload and the latest ECMWF shows a next surge early next week which should bring the coldest air yet down over British Columbia, Montana and Wyoming but this deepeing trough looks to be, more West and Plains, perhaps the Great Lakes and not so much the East, but here, given this setup with the possibility of warm, tropical air flow up the Eastern coastal plain, big multiday rains may occur.

The overall US pattern has changed after the early October cold outbreak. Since October 1, there have been over 2,000 records lows and cold high’s set and since July over 5,000. Talk about a turnaround from the intense heat of June and July.

We shall see over the next couple of weeks more of a western trough and likely eastern ridge. This is the idea outlined in my Fall forecast. Troughiness will intensify in the west as storminess increases. This will allow for a fast start to the snow season throughout the Western ranges.

The latest NAO ensemble shows a drop back to negative but a resurge towards positive in late October but I am suspicious about a week two cold outbreak for a large chunk of the US but will it be east of the Appalachains? I will post later, my thoughts on the remainder of October as well as the Fall across the US, oh and may even add in a few winter hints too… Since you didn’t get this till now. Appologies for that btw, Was annoyed. I had typed this and then the server decided to go down.

Here’s the latest ECMWF charts looking out over the next 10 days.

Notice in the above chart the lack of really cold air. The Pacific flow is dominant and really this is kinda what I envisioned November to be like although a trough would amplify in the West. That certainly looks to happen next week and we may see more and more arctic shots dropping down further west rather than straight into the Plains and East.

It in above chart you can the tightening of the upper winds as a trough can be faintly seen pushing into the Pacific Northwest. Seen much clearer on surface maps.

By Thursday there’s no disputing where the storm is. Check that out. Watch out from Plains to Ohio Valley, could see a rash of severe reports from that setup but notice the air mass. It’s not arctic. There’s no connection!

By Saturday, that storm spins across the Lakes, likely bring a cold rain with perhaps some backside flurries across Minnesota and the Upper Lakes but look what’s dropping south from Alaska and the Yukon. Now that’s coming coming..

By Monday and a strong trough drops into the Pacific Northwest but notice the trough over Alaska, not the best setup for the arctic air to flow straight into the PNW and Rockies. However I recon this arctic airt will drop into the Interior NW and Northern Rockies next week presenting daytime highs in the teens and nighttime lows below zero.

Will have more details later today. Stay tuned!

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